1. Field of the Invention
The present invention relates to monolithic ceramic electronic components, such as a monolithic ceramic capacitor provided with internal electrodes composed of a base metal, for example, nickel or a nickel alloy.
2. Description of the Related Art
Various types of monolithic ceramic electronic components provided with a plurality of ceramic layers and internal electrodes formed between the ceramic layers have been commercially available. A typical example thereof is a monolithic ceramic capacitor in which a ceramic dielectric material is used for the ceramic layers.
Conventionally, a noble metal such as palladium or platinum or an alloy thereof is used for internal electrodes in such a monolithic ceramic capacitor because the dielectric material must be fired in air at a temperature as high as approximately 1,300.degree. C. However, such materials for electrodes are very expensive, resulting in an increase in production cost.
In order to reduce the production cost, the use of base metals as materials for internal electrodes in monolithic ceramic capacitors has been implemented, and various types of nonreducing dielectric materials which can be fired in a neutral or reducing atmosphere in order to prevent the electrodes from oxidizing during firing have been developed. Examples of the base metal used for internal electrodes include cobalt, nickel and copper. In view of cost and oxidation resistance, nickel is predominantly used.
There is now a demand for further reduction in size and larger capacitance with respect to monolithic ceramic capacitors, and an increase in dielectric constant and a decrease in thickness have been studied with respect to ceramic dielectric materials, and simultaneously, a decrease in thickness has been studied with respect to materials for electrodes.
In general, internal electrodes of monolithic ceramic capacitors are formed by a printing method, such as screen-printing, using a paste containing a metallic powder. When nickel powder is used as the metallic powder to be incorporated in such a paste, a nickel powder having an average particle diameter of more than 0.25 .mu.m, which is produced by a liquid phase method or a chemical vapor method, is used in many cases. However, with such a large particle size, it is difficult to decrease the thickness of internal electrodes.
When a nickel powder having an average particle diameter as large as 0.25 .mu.m is used, in order to make the dielectric ceramic exhibit dielectric properties, the thickness of the electrodes must be set at 0.8 .mu.m or more.
Although a decrease in the thickness of the ceramic dielectric layer is the most effective means to increase the capacitance of the monolithic ceramic capacitor, for example, if the thickness of the ceramic layer is 3 .mu.m or less against the thickness of 0.8 .mu.m of the internal electrode, delamination, which is a fatal structural defect in the monolithic capacitor, frequently occurs due to a difference in shrinkage factor between the electrode and the ceramic.
With respect to high dielectric constant type monolithic ceramic capacitors satisfying F-level and E-level characteristics and temperature-compensating type monolithic ceramic capacitors satisfying SL-level and CG-level characteristics stipulated in the Japanese Industrial Standard (JIS), if the thickness of the ceramic layer is as thin as 3 Mm or less, the electrical characteristics may degrade, resulting in difficulty in obtaining a high-performance monolithic ceramic capacitor.